I’ll admit it: I’m a bit slow when it comes to the shell. I use it a lot, but never feel like I’m using it as well as I could. But today, I figured out how to turn on Z Shell completion system. And it is very, very good.

[Bad link] helped me, leading me to add the following to my .zshrc file:

autoload -U compinit
compinit

Once I’d done that, I could begin completing various commands and parameters. Within a few moments, using the tutorial above, I’d already completed:

command names

file and directory paths

changing a directory with cd, listing only directories

listing each directory that would be extracted from a tar archive

ssh destination, including user and host

changing to a directory three-levels deep with cd, using only the first letter of each of the three paths (i.e. “/u/l/b” for “/usr/local/bin”).

When scripting for system administration, it’s often helpful to know what edition and version of Mac OS X is installed.

By edition, I mean whether you are using Mac OS X or Mac OS X Server — Server generally being a superset of the client operating system. The version, of course, is an indentifier such as “10.4.9” or “10.3” or “10.2.8.”

Given the version number, you can deduce the marketing name of the system software: “Tiger,” “Panther,” and “Jaguar,” respectively. Interestingly, I’m aware of no string in the system that identifies that marketing name; even “About This Mac” in the Apple menu does not display it. (However, you can find all of the names in the [Bad link].)

You can obtain the version information in a number of ways. From a scriptability standpoint, the quickest way to the chase is probably the sw_vers utility. The basic usage and output looks like this:

… but you can also, as of Mac OS X 10.3 or later, narrow it down to get just the string you want. (Note that you can only run sw_vers, without modification, in Jaguar and earlier.) So, if you just need the ProductVersion, ask for it:

$ sw_vers -productVersion
10.4.9

One drawback of this solution is that you can only get the version information for a running copy of Mac OS X. According to its man page, sw_vers
“prints version information about the Mac OS X or Mac OS X Server operating
system running on the local machine.” It can’t detect the version of a
non-running Mac OS X installation.

Happily, the same information is stored in two property list files in the /System directory. Therefore, you can read the version data directly from these plist files.

… where $volume is the path to the target volume. The ServerVersion.plist file does not exist on workstation/client edition of Mac OS X. The mere presence of the ServerVersion.plist, therefore, indicates that you have encountered Mac OS X Server.

Reading the plists comes in handy if you’re trying to detect the version of Mac OS X on a disk other than the current startup disk, where sw_vers fails. This means you can even detect the version of Mac OS X installed on Apple’s boot CDs and DVDs!

The plist method is also useful if you’re using a scripting language — such as Python, with its [Bad link] (I’m sure there’s something for Perl, too … and you could also try defaults as above) — that can read them. If the files can be read directly, you don’t need to call out to a shell command, even one as simple as sw_vers or defaults, from within the scripting language. That means you won’t be spawning an additional process, and your scripts can therefore gain a slight speed increase.

Update: I did run the same test on a Mac OS X 10.0 install CD from 2001. The results show that you can use the property list reading method to obtain the version information for any release of Mac OS X:

This simply means there are no directories in common in sys.path — the list of directories where modules can be installed — between these two versions of Python. I find that a bit annoying, since I can’t by default count on deploying one module to a single location that will work in both the default and upgraded versions of Python.

That lack of a default common location also has an impact if you’re managing the filesystem with [Bad link].

Yesterday, I thought I’d came across a potential solution to a problem I’d been having with restoring disk images to target drives using Disk Utility. I keep getting error 22, “invalid argument,” when restoring images over HTTP, using Disk Utility on the original Tiger version of the Mac OS X Install DVD.

While there could be [Bad link], restoring the same images locally — over FireWire target disk mode, for example — appears to succeed reliably and repeatedly. (See also [Bad link], where the core error was also not resolved.)

Let’s say that you have your images stored on a Web server — preferably one with some access controls, because you don’t want your system images open to just anyone. That should let you use Apple Software Restore’s HTTP-based image restore feature. You have already prepped the images for ASR, creating them appropriately (possibly through the use of shadow files) and applying the volume-level checksum that is required for block-level restores.

However, let’s assume that your naming convention for system images includes more than one period. After all, you’re creating images for Mac OS X versions like 10.3.9 and 10.4.8 … it’s natural to want to use those version numbers somewhere in your system image names. There’s no sense in changing those periods to some other character, right?

Well, I surmised there might have been a reason to change or remove those periods. I expected that removing — or encoding with %2e (as noted in this [Bad link]) — the periods from a test image’s name would have a beneficial effect, to let me restore it successfully via HTTP. However, it was still a no-go with the encoded characters, so I’m now back where I started. The image restoration works until near the end of the process, and I get error 22 again. Grr.

I’m wondering out loud now whether there’s a problem with automount, since I’ve seen some search results that seem to mention error 22 in conjunction with it. I have no clue why it would fail only for HTTP-based ASR restores using a Tiger install DVD, though.

It seems I can recall the restore-via-HTTP feature working at some point in the past, but it certainly hasn’t done so to my recollection under Tiger.

I don’t recall exactly how I got to this point, but I’d never seen a hint that provided color with this level of ease — and I recently fell into a pique of wanting but not having colorized shell output.

I’d been having problems for several weeks, maybe months, with printing out some kinds of documents from my office MacBook Pro. I’d send the print jobs to our trusty Xerox WorkCentre Pro 55, and I’d get one copy of the document. This was okay when I only wanted one copy. But, I’d increasingly had a need for several … so defaulting to one just made it difficult to get multiple original copies (or “mopies,” I guess, if you subscribe to HP-lingo) when I needed them.

This problem seemed to spread from PDFs in Safari, to all PDFs, and then to other document types — including, most recently, documents printed directly from Microsoft Word 2004. At this point, I became aggravated enough that I tried some very minimal troubleshooting, which quickly led nowhere. I just wanted this to work.

So, I took the shotgun approach. I hate doing this, because I want to know the whys and wherefores of problems. I want to apply the scientific method to finding and resolving the issue at hand. I want to prevent the problem from appearing again. In this case, though, I just needed to print … and I resorted to the “Reset Printing System” menu command in Printer Setup Utility.

I next tried a PDF that had failed to print completely before. I’ve had success with that, as well. Excellent.

Therefore, if you know the definitions for your printers — because the “Reset Printing System” command in Tiger will delete your print queues and force you to re-add them — then the reset option can resolve some strange problems and get you back in working order.

However, if you’re updating images, keeping the base and intermediate images can strain your storage capacity. Mac OS X lacks the compelling live editing features of Microsoft’s new WIM image format — which if it had appeared first on the Mac, I’d be trumpeting loudly, so I feel compelled to at least give a nod to Microsoft here.

Since I’m always struggling with storage capacity and I prefer having an up-to-date base image, I thought about this problem a bit in the context of Mac OS X imaging and have come upon what seems to be a unique solution: the use of shadow files.

Here’s the basic idea:

Create a base operating system install on a partition of your template computer’s disk

Capture a compressed, read-only image of it immediately (go wild, save the extra percent or two, and compress it with the Tiger-only bzip2 scheme … you can afford to do this if you have time and are only deploying with a Tiger startup disk)

Attach that base image to the filesystem — honoring ownership and specifying a shadow file — so that it acts as if it is writable, using hdiutil

Install the latest Mac OS X combo update on it

Create a new read-only compressed image of the mounted volume

Prep the new updated base image for ASR.

Congratulate yourself on this use of shadow files, because you’ve saved at least one intermediate step and the space required for a full read-write disk image — or worse, an extra local partition needed only for restoration and updating the base image.

Unmount that volume and throw away the shadow file at this point if you want, because you’ve now got two system images ready for deployment. One has the base system software, and serves as a checkpoint that you can return to later; it’s the base for all future updates of that major revision of Mac OS X. The other image has the latest version of Mac OS X. If you’re deploying that image with ASR, the result will be a more secure system because it’s closer to being fully patched — and it should take less time to update it with the additional security updates and application installs — whether you use installers or Radmind or another solution — because you’ve got the bulk of the operating system done.

Unfortunately, many updates can only be installed on the startup disk and thus cannot be included in the updated base image. Beyond the combo operating system updates, few of Apple’s other installers will work on a non-startup volume. But you can install them after deploying the updated base image, using your tool of choice. For reasons like this, Geoff doesn’t see updating the base image as valuable, but in some IT environments, it may be very worthwhile.

My next step is to script this process and tie it to a watched folder. Imagine dropping a combo update into a watched folder … and letting a script generate the new, updated image for you.

I can remember how excited I was to get Mac OS X 10.0. I picked it up early, before it was actually supposed to be sold, at [Bad link] in Victor. I even got them to price match to a Web price of $99, but not all the way down to the academic price of $69. I bought it partly for the cachet of getting it early.

I’ve been toying with the idea of using network home directories on my personal systems. I want to have the same home directory on every computer, but I don’t want to have to mount it entirely over my network. So, a mobile home directory, with home directory sync to my Infrant ReadyNAS NV+, sounds like an interesting solution.

Unfortunately, I lack a directory service that I could use as a data source for the right attributes. I simply don’t have an Active Directory or Open Directory at home. Nor, really, do I want to run one — especially since I’d have to explain to my lovely and far-too-understanding wife why I can’t recycle an old computer that she would love for me to get rid of. Grin.

On the other hand, I do have the ReadyNAS, so I do have storage for my home directories. Even if the ReadyNAS’ AFP support is not the fastest, it’s still there and running all the time. Actually, given the performance of AFP on it, home directory sync probably is a better solution than an all-out network home directory setup.

So, the idle thought hit me the other day: why not create a phantom directory service, using DirectoryService’s ability to handle static mappings? I’d just need to define a directory that has no directory server, create static mappings for the right attributes, and use the relatively new variable substitution feature for static mappings to get the home directory attribute set up correctly for each local user account on the system. The main trick, as I can see it, is that the UID and GID for my local accounts is not necessarily consistent between computers.

I haven’t tried it, but it suuure sounds promising when the idea is rattling in my head. Hm.

I’ve tried both alternatives — the built-in keywording UI, and the freeware Keyword Assistant — and neither has been entirely satisfactory. Of course, I now have those experiences to compare against the much more effortless tagging in the current Del.icio.us interface, which is one of the most fluid keywording interfaces I’ve used yet. I don’t know if Keyword Manager will be an improvement (especially one that is almost half my cost for the iLife suite), but it has promise that it could be.